From 06811ced27d809610cfde1db85dd138452f40436 Mon Sep 17 00:00:00 2001 From: Hanno Becker Date: Wed, 3 May 2017 15:10:34 +0100 Subject: [PATCH] Put configuration options for RSA blinding and verification to work. --- library/rsa.c | 132 +++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 108 insertions(+), 24 deletions(-) diff --git a/library/rsa.c b/library/rsa.c index c8090044a..d3feeba88 100644 --- a/library/rsa.c +++ b/library/rsa.c @@ -398,24 +398,68 @@ int mbedtls_rsa_private( mbedtls_rsa_context *ctx, { int ret; size_t olen; - mbedtls_mpi T, T1, T2; + + /* Temporary holding the result */ + mbedtls_mpi T; + + /* Temporaries holding P-1, Q-1 and the + * exponent blinding factor, respectively. */ mbedtls_mpi P1, Q1, R; -#if defined(MBEDTLS_RSA_NO_CRT) - mbedtls_mpi D_blind; - mbedtls_mpi *D = &ctx->D; -#else + +#if !defined(MBEDTLS_RSA_NO_CRT) + /* Temporaries holding the results mod p resp. mod q. */ + mbedtls_mpi TP, TQ; + + /* Temporaries holding the blinded exponents for + * the mod p resp. mod q computation (if used). */ mbedtls_mpi DP_blind, DQ_blind; + + /* Pointers to actual exponents to be used - either the unblinded + * or the blinded ones, depending on the presence of a PRNG. */ mbedtls_mpi *DP = &ctx->DP; mbedtls_mpi *DQ = &ctx->DQ; +#else + /* Temporary holding the blinded exponent (if used). */ + mbedtls_mpi D_blind; + + /* Pointer to actual exponent to be used - either the unblinded + * or the blinded one, depending on the presence of a PRNG. */ + mbedtls_mpi *D = &ctx->D; +#endif + +#if defined(MBEDTLS_RSA_REQUIRE_VERIFICATION) + /* Temporaries holding input mod p resp. mod q. */ + mbedtls_mpi IP, IQ; + + /* Temporaries holding double check results mod p resp. mod q; + * should in the end have the same values as IP and IQ. */ + mbedtls_mpi CP, CQ; + + /* Comparison results */ + int check = 0; +#endif + +#if defined(MBEDTLS_RSA_FORCE_BLINDING) + if( f_rng == NULL ) + return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); #endif /* Make sure we have private key info, prevent possible misuse */ if( ctx->P.p == NULL || ctx->Q.p == NULL || ctx->D.p == NULL ) return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); - mbedtls_mpi_init( &T ); mbedtls_mpi_init( &T1 ); mbedtls_mpi_init( &T2 ); - mbedtls_mpi_init( &P1 ); mbedtls_mpi_init( &Q1 ); mbedtls_mpi_init( &R ); +#if defined(MBEDTLS_THREADING_C) + if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 ) + return( ret ); +#endif + /* MPI Initialization */ + + mbedtls_mpi_init( &T ); + + mbedtls_mpi_init( &P1 ); + mbedtls_mpi_init( &Q1 ); + mbedtls_mpi_init( &R ); if( f_rng != NULL ) { @@ -427,12 +471,17 @@ int mbedtls_rsa_private( mbedtls_rsa_context *ctx, #endif } - -#if defined(MBEDTLS_THREADING_C) - if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 ) - return( ret ); +#if !defined(MBEDTLS_RSA_NO_CRT) + mbedtls_mpi_init( &TP ); mbedtls_mpi_init( &TQ ); #endif +#if defined(MBEDTLS_RSA_REQUIRE_VERIFICATION) + mbedtls_mpi_init( &IP ); mbedtls_mpi_init( &IQ ); + mbedtls_mpi_init( &CP ); mbedtls_mpi_init( &CQ ); +#endif + + /* End of MPI initialization */ + MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &T, input, ctx->len ) ); if( mbedtls_mpi_cmp_mpi( &T, &ctx->N ) >= 0 ) { @@ -440,6 +489,11 @@ int mbedtls_rsa_private( mbedtls_rsa_context *ctx, goto cleanup; } +#if defined(MBEDTLS_RSA_REQUIRE_VERIFICATION) + MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &IP, &T, &ctx->P ) ); + MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &IQ, &T, &ctx->Q ) ); +#endif + if( f_rng != NULL ) { /* @@ -498,24 +552,25 @@ int mbedtls_rsa_private( mbedtls_rsa_context *ctx, /* * Faster decryption using the CRT * - * T1 = input ^ dP mod P - * T2 = input ^ dQ mod Q + * TP = input ^ dP mod P + * TQ = input ^ dQ mod Q */ - MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &T1, &T, DP, &ctx->P, &ctx->RP ) ); - MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &T2, &T, DQ, &ctx->Q, &ctx->RQ ) ); + + MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &TP, &T, DP, &ctx->P, &ctx->RP ) ); + MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &TQ, &T, DQ, &ctx->Q, &ctx->RQ ) ); /* - * T = (T1 - T2) * (Q^-1 mod P) mod P + * T = (TP - TQ) * (Q^-1 mod P) mod P */ - MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( &T, &T1, &T2 ) ); - MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &T1, &T, &ctx->QP ) ); - MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &T, &T1, &ctx->P ) ); + MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( &T, &TP, &TQ ) ); + MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &TP, &T, &ctx->QP ) ); + MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &T, &TP, &ctx->P ) ); /* - * T = T2 + T * Q + * T = TQ + T * Q */ - MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &T1, &T, &ctx->Q ) ); - MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &T, &T2, &T1 ) ); + MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &TP, &T, &ctx->Q ) ); + MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &T, &TQ, &TP ) ); #endif /* MBEDTLS_RSA_NO_CRT */ if( f_rng != NULL ) @@ -528,6 +583,23 @@ int mbedtls_rsa_private( mbedtls_rsa_context *ctx, MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &T, &T, &ctx->N ) ); } + /* If requested by the config, verify the result to prevent glitching attacks. + * For that, check the two prime moduli separately. */ +#if defined(MBEDTLS_RSA_REQUIRE_VERIFICATION) + MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &CP, &T, &ctx->E, &ctx->P, &ctx->RP ) ); + MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &CQ, &T, &ctx->E, &ctx->Q, &ctx->RQ ) ); + + check |= mbedtls_mpi_cmp_mpi( &CP, &IP ); + check |= mbedtls_mpi_cmp_mpi( &CQ, &IQ ); + + if( check != 0 ) + { + /* Verification failed */ + ret = MBEDTLS_ERR_RSA_VERIFY_FAILED; + goto cleanup; + } +#endif /* MBEDTLS_RSA_REQUIRE_VERIFICATION */ + olen = ctx->len; MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &T, output, olen ) ); @@ -537,8 +609,9 @@ cleanup: return( MBEDTLS_ERR_THREADING_MUTEX_ERROR ); #endif - mbedtls_mpi_free( &T ); mbedtls_mpi_free( &T1 ); mbedtls_mpi_free( &T2 ); - mbedtls_mpi_free( &P1 ); mbedtls_mpi_free( &Q1 ); mbedtls_mpi_free( &R ); + mbedtls_mpi_free( &P1 ); + mbedtls_mpi_free( &Q1 ); + mbedtls_mpi_free( &R ); if( f_rng != NULL ) { @@ -550,6 +623,17 @@ cleanup: #endif } + mbedtls_mpi_free( &T ); + +#if !defined(MBEDTLS_RSA_NO_CRT) + mbedtls_mpi_free( &TP ); mbedtls_mpi_free( &TQ ); +#endif + +#if defined(MBEDTLS_RSA_REQUIRE_VERIFICATION) + mbedtls_mpi_free( &IP ); mbedtls_mpi_free( &IQ ); + mbedtls_mpi_free( &CP ); mbedtls_mpi_free( &CQ ); +#endif + if( ret != 0 ) return( MBEDTLS_ERR_RSA_PRIVATE_FAILED + ret );